Field of the Invention
The present invention relates to data storage devices, and in particular, relates to FLASH memory control methods.
Description of the Related Art
A FLASH memory is a general non-volatile storage device that is electrically erased and programmed.
A NAND FLASH, for example, is primarily used in memory cards, USB FLASH devices, solid-state drives, and so on. In a multi-chip package, a NAND FLASH and a controller chip may be packaged into a single package as an eMMC (embedded MultiMediaCard).
In a NAND FLASH, the storage array comprises a plurality of blocks and each block comprises a plurality of pages. Some blocks are allocated to be data blocks, and, the blocks waiting for allocation may be spare blocks. Depending on usage situations, some of the storage space may be damaged. The damaged blocks should not be utilized anymore. Thus, the available number of spare blocks may decrease. When the total amount of spare blocks is less than a threshold amount, the FLASH memory should be tagged as: End-of-Life. If tagged, no more write operations is allowed and the FLASH memory is switched to a read-only mode.
It is an important topic in the field to prolong the lifespan of a FLASH memory for normal read/write operations.